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Once again, I have a couple of questions:

1. We have object where I use v570+ATC8. To ATC8 connected 4xTC and 4xAI(4-20mA). I sent specifications to our TC manufacturer and they made 3 TC (K type) sensors of water temperature and 1 TC (K- type) sensor of outdoor temperature. Water sensors are connected with K-type compensating cable (~10m each) and outdoor sensor also with K-type compensating cable ~40m long. When powered, water temperature indication is alright, but outdoor temperature (when in real was 8C) at once showed about 20C, then began to drop and after about couple hours it was indicating ~12C. Why is this error? Because of cable length or it has something to do with sensor? We changed sensor, but it's the same...

2. With the same ATC8, there are connected 4 AI (4-20mA): 2 inputs are speeds of 2xFC, and 2 inputs are the position of valves. FC's are 7.5kw and 2.2kw. They are mounted in cabinet, that stand next to PLC's cabinet (signal cable lenght ~3-4m.). In OFF mode, FC's are powered up, but pumps are not connected (with MC's) to FC output, in RUN mode pump (pumps never work together, but working pump is chosen by season) are connected to FC output. So there's an issue: In fast mode (819 to 4095) of valves position AI, when pump (7.5kW) is not connected to FC , AI's min value shows ~820 units, when pimp connected it drops down to 738 units (when valve closed) when valve is open it shows ~4096 units in both ways. Other valves AI's min value also drops down, but not that much. Is there's any thoughts about this? Checked the groundin, everything seems fine..

Thank you


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AI of IO-ATC8 are not isomlated. It seesm there is a current loop, or a strong noise when the pump is running.

Do you have good grounding point in both cabinets?

Is the controller and the power supply grounded properly?

If you will keep the sensors in the air - not touching objects or liquids, whch are in touch with ground - is the problem still occure?

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